What is Analgelin (Metamizole)?
Analgelin is a brand name for the drug Metamizole, also known as dipyrone [1.2.1]. It is a non-opioid analgesic with strong pain-relieving (analgesic), fever-reducing (antipyretic), and muscle-relaxing (spasmolytic) properties [1.4.1]. Belonging to the pyrazolone class of medicines, it is considered a potent option for managing moderate to severe pain [1.2.4].
Despite its effectiveness, Metamizole is the subject of significant global controversy. Its use has been banned in many countries, including the United States, United Kingdom, Canada, and Australia, due to its association with a rare but potentially fatal side effect called agranulocytosis [1.6.1, 1.6.4, 1.6.7]. However, it remains a widely prescribed and even over-the-counter medication in other parts of the world, such as Germany, Spain, Russia, Mexico, and much of South America [1.2.1, 1.2.6].
Mechanism of Action: How Does Analgelin Work?
The precise mechanism of action for Metamizole is complex and not fully understood [1.4.4]. It is considered a pro-drug, meaning it is hydrolyzed in the gastrointestinal tract into its primary active metabolite, 4-methyl-amino-antipyrine (MAA) [1.4.7]. The drug's effects are believed to stem from several pathways:
- Inhibition of Prostaglandin Synthesis: Metamizole and its metabolites inhibit cyclooxygenase (COX) enzymes, particularly COX-2, which are involved in the synthesis of prostaglandins. Prostaglandins are compounds that mediate pain and fever in the body [1.4.2]. This action is similar to other non-steroidal anti-inflammatory drugs (NSAIDs), though Metamizole generally shows weaker anti-inflammatory properties [1.4.3].
- Activation of Cannabinoid and Opioid Systems: Some research suggests that Metamizole's analgesic effect may also involve the activation of the body's own cannabinoid (CB1) and opioidergic systems [1.4.1, 1.4.6].
- Spasmolytic Effect: Its ability to relieve spasms, such as in cases of colic, is thought to be related to the inhibition of calcium release in smooth muscle cells [1.4.2].
Primary Clinical Uses of Analgelin
Due to its potency and risk profile, Metamizole is typically reserved for specific, severe conditions where other analgesics are ineffective or contraindicated [1.4.3]. Its approved uses in countries where it is available include:
- Severe Acute Pain: This is the most common indication, particularly for post-operative pain following surgery or pain from acute injuries [1.2.6, 1.4.3].
- Colic Pain: It is effective in treating visceral pain caused by spasms in the gastrointestinal or biliary tracts [1.2.6].
- Cancer-Related Pain: Metamizole is used in oncology for managing moderate to severe tumor-related pain [1.4.3].
- High Fever: It is indicated for treating high fever (pyrexia) that does not respond to other antipyretic medications like paracetamol or ibuprofen [1.2.6].
It is administered orally (tablets, drops), rectally (suppositories), or via injection [1.2.1]. Dosage varies significantly based on the condition, patient's age, and country's regulations, and must be determined by a healthcare professional.
Understanding the Risks: Agranulocytosis and Other Side Effects
The primary reason for the strict regulation and banning of Metamizole in numerous countries is its association with agranulocytosis. It is crucial for anyone considering this medication to understand this risk.
The Life-Threatening Risk of Agranulocytosis
Agranulocytosis is a severe and sudden drop in the number of a specific type of white blood cell called neutrophils [1.5.1]. Neutrophils are a critical part of the immune system's defense against infection. Without them, the body is highly susceptible to life-threatening bacterial infections and sepsis [1.5.4].
- Incidence: The estimated risk varies widely in studies, from as low as 1 case per million users to as high as 1 case per 1,439 prescriptions [1.5.4].
- Mechanism: The exact cause is not fully understood but is believed to be an immune-mediated reaction or a direct toxic effect on bone marrow precursors [1.5.3, 1.5.4]. It is not considered a dose-dependent reaction, meaning it can occur at any dose and at any time during treatment, even after previous problem-free use [1.5.1].
- Symptoms: Patients are warned to immediately seek medical help if they experience symptoms like fever, chills, persistent sore throat, exhaustion, and painful sores or inflammation in the mouth or throat [1.5.1].
Other Potential Side Effects
Beyond agranulocytosis, Metamizole is associated with other adverse effects:
- Hypotension: Drops in blood pressure, especially with intravenous administration [1.2.1].
- Allergic Reactions: Skin rashes, urticaria (hives), and in rare cases, severe anaphylactic shock [1.2.1, 1.2.3].
- Liver Injury: Cases of drug-induced liver injury, some severe enough to require liver transplantation, have been reported [1.2.1].
- Gastrointestinal Issues: While often considered to have better gastrointestinal tolerability than traditional NSAIDs, it can still cause issues like nausea [1.2.1, 1.2.4].
Comparison with Common Pain Relievers
| Feature | Metamizole (Analgelin) | Ibuprofen (Advil, Motrin) | Paracetamol (Acetaminophen) | Aspirin |
|---|---|---|---|---|
| Type | Pyrazolone non-opioid | NSAID | Analgesic, Antipyretic | NSAID, Salicylate |
| Primary Use | Severe pain, refractory high fever, colic [1.2.6] | Mild to moderate pain, inflammation, fever | Mild to moderate pain, fever | Pain, fever, anti-platelet (heart health) |
| Key Benefit | Potent analgesic and spasmolytic effects [1.2.6] | Good anti-inflammatory effect | Generally safe on the stomach | Cardiovascular protection at low doses |
| Major Risk | Agranulocytosis (rare but fatal), liver injury [1.2.1, 1.5.6] | Stomach ulcers, kidney problems, cardiovascular risk | Liver damage in overdose | Stomach bleeding, Reye's syndrome in children |
Conclusion
What is the use of Analgelin? It is a powerful analgesic and antipyretic (Metamizole) reserved for severe pain and fever that do not respond to other treatments [1.2.1, 1.2.6]. While effective and widely used in many parts of the world, its utility is overshadowed by a rare but serious risk of agranulocytosis, a potentially fatal blood disorder [1.5.4]. The starkly different regulatory statuses across the globe—banned in countries like the US and UK while being a common painkiller in others—highlight the ongoing medical debate about its risk-benefit profile [1.6.1, 1.6.2]. Due to these dangers, Metamizole should only ever be used under the strict guidance and supervision of a healthcare professional in countries where it is legally approved. For more information on its regulatory status, one might consult the European Medicines Agency [1.2.7].
